#include <stdio.h>
#include <ctype.h>

//E -> TE' 
//E' -> +TE' | e
//T -> FT'
//T' -> *FT' | e
//F -> NUM | (E)
//FIRST(E) = {NUM, LEFTB}
//FIRST(E') = {PLUS, e}
//FIRST(T) = {NUM, LEFTB}
//FIRST(T') = {MULT, e}
//FIRST(F) = {NUM, LEFTB}
//FOLLOW(E) = {$, RIGHTB}
//FOLLOW(E') = {$, RIGHTB}
//FOLLOW(T) = {PLUS, RIGHTB, $}
//FOLLOW(T') = {PLUS, RIGHTB, $}
//FOLLOW(F) = {MULT, PLUS, RIGHTB, $}

enum TOKEN { PLUS, MULT, NUM, END, ERR, LEFTB, RIGHTB };
char lookahead;
enum TOKEN token;
int num;
int error = 0;
FILE *fp;


void lexical(FILE *fp);
int match(enum TOKEN x);
int E();
int E_();
int T();
int T_();
int F();





//return 0 if success, return 1 otherwise
int match(enum TOKEN x) {
	if (token == x) {
		lexical(fp);
		return 0;
	}
	else {
		error = 1;
		return 1;
	}
}



//E -> TE' 
int E() {
	return T() + E_();
}



//E_ -> +TE'|e 
int E_() {
	if (lookahead == '+')
	{
		match(PLUS);
		return T() + E_();
	}
	else
	{
		return 0;
	}
	return 0;
}



//T -> FT'
int T() {
	int sum = F()*T_();
	return sum;
}





//T' -> *FT' | e
int T_() {
	if (lookahead == '*')
	{
		match(MULT);
		return F()*T_();
	}
	else
	{
		return 1;
	}
}



//F -> NUM | (E)
int F() {
	if (num != 0)
	{
		int sum = num;
		match(NUM);
		return sum;
	}
	else if (lookahead == '(')
	{
		match(LEFTB);
		int sum = E();
		match(RIGHTB);
		return sum;
	}
	else
	{
		error = 1;
	}
	return 0;
}



void lexical(FILE *fp) {

	lookahead = getc(fp);
	num = 0;
	while (lookahead == ' ' || lookahead == '\t' || lookahead == '\n') {
		lookahead = getc(fp);
	}

	if (isdigit(lookahead)) {
		num = 0;
		while (isdigit(lookahead)) {
			token = NUM;
			num = num * 10 + lookahead - '0';
			lookahead = getc(fp);
		}
		ungetc(lookahead, fp);
		return;
	}
	else if (lookahead == '+') {
		token = PLUS;
		return;
	}
	else if (lookahead == '*') {
		token = MULT;
		return;
	}
	else if (lookahead == EOF) {
		token = END;
		return;
	}
	else if (lookahead == '(') {
		token = LEFTB;
		return;
	}
	else if (lookahead == ')') {
		token = RIGHTB;
		return;
	}
	else {
		error = 1;
		token = ERR;
		return;
	}
}



int main(int argc, char **argv) {
	int  res = 0;
	if (argc < 2) {
		printf("insufficient arguments");
		return 1;
	}
	fp = fopen(argv[1], "r");
	lexical(fp);
	res = E();
	if (!error) {
		printf("%d\n", res);
	}
	else {
		printf("There are errors\n");
	}
	fclose(fp);
	return 0;
}

